Spreading type disk brake



June 22, 1965 E. R. EVANS SPREADING TYPE DISK BRAKE ori inal Filed March7, 1956 5 Sheets-Sheet 1 INVENTOR. EDWIN R.EVA NS. WW /W y June 22, 1965E. R. EVANS 3,190,398

SPREADING TYPE DISK BRAKE Original Filed March 7, 1956 5 Sheets-Sheet 2'INVENTOR. EDWIN REV/4N5.

135E mz mwww E. R. EVANS SPREADING TYPE DISK BRAKE June 22, 1965 5Sheets-Sheet 5 Original Filed March 7. 1956 INVENTOR. EDWIN R EVA NSJune 22, 1965 EVANS 3,190,398

SPREADING TYPE DISK BRAKE Original Filed March 7, 1956 5 Sheets-Sheet 4IN VEN TOR.

EDWIN R. EVANS.

June 22, 1965 E. R. EVANS SPREADING TYPE DISK BRAKE 5 Sheets-Sheet 5Original Filed March 7, 1956 mmvrox sow/1v R. EIYZA us.

United States Patent O 3,190,398 SPREADING TYPE DISK BRAKE Edwin R.Evans, Orchard Lake, Mich; The Detroit Bank and Trust Company, executorof said Edwin R. Evans, deceased Original application Mar. 7, 1956, Ser.No. 570,064, new Patent No. 2,999,565, dated Sept. 12, 196i. Divided andthis application July 24, 1961, Ser. No. 126,104 3 Claims. (Cl. 188-72)This is a division of application Serial No. 570,064, filed March 7,1956, and now Patent No. 2,999,565.

The invention relates to disk brakes and refers more particularly todisk brakes for use with motor vehicle wheels.

The invention has for one of its objects to provide an eflicient diskbrake, the parts of which are simple in construction. and may be cheaplymanufactured.

The invention has for another object to provide a disk brake, the partsof which may be readily assembled.

The invention has for still other objects to provide a disk brakecomprising a rotatable member, a pair of brake elements engageable withaxially spaced disks of the rotatable member and a single anchor for thebrake elements; to provide a disk brake in which one brake eletfl mentis mounted on the anchor and the other of the brake elements is mountedon the first brake element; to provide means for moving the brakeelements into engagement with the disks comprising a lever, a fluidpressure cylinder and a piston within the cylinder for moving the lever,the lever and cylinder acting on one brake element and the lever aloneacting on the other brake element to move these brake elements away fromeach other and into engagement with the disks; to provide a disk brakein which the brake elements, lever and anchor are formed to hold theparts from radial movement as well as circumferential movement; and toprovide a disk brake in which flexing of the rotatable member uponfrictional engagement of its disks by the brake elements is limited tothereby provide for decreasing the weight of the rotatable memberwithout increasing the risk of damaging the rotatable member.

The invention has for further objects to utilize the means for limitingthe flexing of the rotatable member as an additional brake element; toso arrange the means for limiting the flexing that it, in effect, formswith the disks and brake elements a triple disk brake; to mount themeans for limiting the flexing on the anchor for the brake elements; andto provide a simple self-locking and measuring adjustment means for themeans for limiting the With these as well as other objects in view, theinvention resides in the novel features of construction and combinationsand arrangements of parts as more fully hereinafter set forth.

FIGURE 1 is an outboard elevation partly broken away and in section of abrake embodying the invention;

FIGURE 2 is an enlarged view similar to FIGURE 1;

FIGURES 3 and 4 are enlarged cross sections on the lines 3-3 and 44respectively of FIGURE 1;

FIGURES 5, 7, 8 and 9 are cross sections on the lines 55, 77, 8-8 and 99respectively of FIGURE 2;

FIGURE 6 is a cross section on the line 66 of FIGURE 3;

FIGURES 10 and 11 are elevations of opposed surfaces of the inner andouter brake elements respectively;

FIGURE 12 is a digrammatic view illustrating the method of securing thelocus on the lining of a brake element on which the brake applyingforces are exerted to assure uniform wear of the lining.

The brake illustrated in FIGURES 1 to 12 inclusive is 'ice a disk brakefor use with a front wheel of a motor vehicle.

The disk brake comprises the rotatable member 1, the inner and outerbrake elements 2 and 3, respectively the actuating mechanism 4 formoving the brake elements into engagement with the rotatable member andthe anchor 5 for the brake elements.

The rotatable member 1 is a one-piece radially inwardly opening brakedrum having the axially spaced inner and outer disks 6 and 7,respectively, providing opposed brake surfaces for the brake elements,the peripheral portion 8 connecting the disks and the web 9 extendinggenerally radially inwardly from the outer disk 7. The brake drum isreinforced by the ribs 10 having axial portions extending radiallyoutwardly from the peripheral portion 8 and radial portions extendingaxially inwardly and outwardly from the disks 6 and 7 respectively. Thebrake drum is also reinforced by the annular ribs 11 extending axiallyinwardly and outwardly from the disks 6 and 7, respectively, and furtherreinforced by the radial ribs 12 extending axially outwardly from theradially outer portion of the web 9. The brake drum is detachablymounted on a front wheel hub 13 of the motor vehicle by suitablymounting and securing the web 9 on the fixed flange 14 of the wheel hubin a conventional manner.

The inner and outer brake elements 2 and 3, respectively, are frictionmembers which extend within the brake drum between the inner and outerdisks 6 and 7 respectively and are engageable with their respectivebrake surfaces. The inner and outer brake elements have the bodies 15which are formed with the coextensive generally arcuate portions 16providing flat surfaces to which are secured the arcuate linings 17 forengaging the brake surfaces of the disks 6 and 7. The arcuate portionsand lining are sectors and extend circumferentially of the disks arelatively short distance so that the brake elements are brake shoes.

The actuating mechanism 4 for axially moving the brake shoes away fromeach other and into frictional engagement with the disks comprises thelever 18 and the fluid pressure operated actuator 19 having thehydraulic cylinder 20, the piston 21, and the piston rod 22. The leveris a plate, preferably formed of steel, extending between the brakeshoes 2 and 3 and pivotally connected at its radially inner end to thepiston rod 22. The lever has the cam surface 23 and 24 for engaging thereinforcing ribs 25 and 26 of the inner and outer brake shoes 2 and 3respectively when forcing the brake shoes against their respectivedisks. The ribs 25 and 26 extend chordwise of the body portions 16 andare integral with the inner and outer brake shoes respectively, the rib25 being located radially outwardly of the rib 26. The body 15 of theinner brake shoe 2 also has the central portion 27 which extendsradially inwardly from the arcuate portion 16 and carries the actuator19. As shown, the hydraulic cylinder of the actuator is secured bysuitable bolts 28 to the central portion and extends axially inwardlythrough the central opening in the inner disk 6. The piston 21 has arecessed end providing a partly spherical seat for the piston rod 22.

The ribs and 26 extend throughout the major chordwise extent of thebodies 16 and the cam surfaces 23 and 24 extend throughout the width ofthe lever 18 and are coextensive with the ribs so that the ribs and camsurfaces have extended linear contact. Both the inner and outer brakeshoes and the lever are constructed to have great rigidity and the leverserves to increase the rigidity of the shoes so that the brake shoes maybe formed of cast iron. The arrangement is such as to provide themaximum lining pressure with the minimum of strain in the assembly andto provide a much desired 3 saving in fluid displacement. the contactingsurfaces is unnecessary as proven by the fact that no appreciable Wearat the contacting surfaces.

was found after many thousands of brake applications.

The actuating mechanism presents a closed system in which the hydrauliccylinder 2% and the lever 13, upon entrance of fluid under pressure intothe hydraulic cylinder, exerts force in an inboard or axiallyinner-direction upon the central and radially outer arcuate portions 27and 16 respectively of the inner brake shoe 2 and the lever exerts forcein an outboard or axially outer direction upon the outer brake shoe 3between the radially inner end of the lever and the line of contact ofthe lever upon the inner brake shoe. Therefore, with a 3 to 1 leverratio, the effort exerted upon each of the brake shoes forcing the sameaway from each other and against the disks is four times the pressureexerted by the fluid in the hydraulic cylinder. Furthermore, thepressure exerted upon the outer brake shoe is along the chordal linepresented by the rib 26 and the pressure exerted upon the inner brakeshoe is equal to and opposite that exerted upon the chordal line of theouter brake shoe. This pressure upon the outer brake shoe 3 along thechordal line presented b y the rib 26 is the only brake applyingpressure acting on shoe 3 and therefore is the resultant force thereon.The resultant force upon the inner brake shoe 2, which, as indicated-isequal to and opposite that exerted on the outer shoe 3, is theresultantof the two pressures exerted upon the inner shoe, namely, thepressure along the chordal' line presented by rib25 and the pressure ofthe actuator cylinder 20 upon the central portion 27.

Wear of the lining is a product of'pres su're'times ve-' :locityand,.for the purpose of equally distributing the lining wear, the lineof contact between the rib 26 and the lever 18 must be located so thatthe product of pressure (P and velocity (V at one radial side of thelineequalsthe product of pressure (P and velocity (V at theothe'r radialside of the line, or P V =P V In order to secure this result, thelocation of the line of contact and, consequently, the location of thechordal rib of the outer brake shoe can be secured by developing aformula as follows:

Given: The inner and outer radii of the lining and the included anglewhich the lining subtends.

- Symbols used:

Ttorque, lb. in. F,friction force, lb. F axial force, lb. r mean radius,in. f--coefiicient of friction r inner radius of lining, in. r outerradius of lining, in. p-unit pressure, p.s.i. V-velocity of rubbingK-constant C-constant In order that all of the surface will remain incontact the wear in the axial direction must be the same for all valuesof r. Wear is proportional to the work done by friction, which is inturn proportional to'the product of the normal pressure and thevelocityof rubbing.

Therefore:

W=wear=Kpv=Kpr since the rubbing velocity varies as the radius, r.

Then

' where C is a constant, since W and K are constants:

Also, surface hardening of Substituting p for its value C/ r 21r 1r(ML-732) -a i The total axial force,

sum of the inner and outer radii. This means that if the leverforces canbe distributed along the mean radius, uniform wear will result takinginto account the increased rubbing velocity toward the outer peripheryof the lining. The angle subtended by the circular segment does noteffect the mean radius. 7

Referring to FIGURE 12 of the drawings: 7

Assume a force, P which when applied at a distance d 7 will bedistributed along the mean radius, r

7 gaged by the axially extending extensions 34 on the trans- The locusupon which the lever forces may be applied so as to insure uniform wearupon a circular segment is therefore, the centroidal axis 0 fthe meanradius, r which is a'circular arc.

The centroidal axis for any circular arc is given by the formula:

R sin la I %a in radians Where:

d=the distance. between the centroidal axis and the center of thecircular arc.

R=radius of the circular arc.

a=angle subtended by the, circular arc.

For any, circular segment the locus upon which the lever I forces may beapplied. so as to assure uniform wear is:

7 sin %o: }cg in radians Where The anchor 5 is a bracket secured, as bymeans of the bolts 29 to thefiange 3b of a conventional front wheelspindle. The anchor bracket serves as a mounting for the inner brakeshoe;2 and limits circumferential movement and radial movementbut'provides for axial movement of this brake shoe. More in detail, theanchor bracket has the body 31 provided with the circumferentiallyspaced arms 32. The arms are formed with the transverse grooves 33opening toward each other in a direction chordwise of the brake andthese grooves are slidably enthe bowed spring 36 is provided between thebottom of the groove and the associated extension facing in a directionopposite the forward direction of rotation of the brake drum asindicated by the arrow 37 in FIGURES 1 and 2. The ends of the spring arereturn-bent and engage recesses in the sides of the anchor bracket. Thearms and end extension are of material width axially of the brake sothat the anchor bracket serves to hold the inner brake shoe fromtwisting in the brake drum. Also, the construction is such that thebottoms and overhanging parts of the grooves respectively serve to limitcircumferential and radial movement of the inner brake shoe.

The lever 18 has the axially aligned pintles 38 at its edges which arejournaled in the pair of bearings 39 and the pair of bearings 40. Thebearings 39 have radially inner and outer arcuate surfaces of the sameradii axially slidably engaging corresponding surfaces of the radiallyinner and outer flanges 41 and 42 respectively which extend transverselyof the body portion 16 of the inner brake shoe 2. The bearings 40 havearcuate surfaces axially slidably engaging arcuate surfaces of thesemicircular flanges 43 which extend transversely of the body portion 16of the outer brake shoe 3 and face or open toward each other. Thebearings 39 and 40 are preferably formed from cylindrical rods fashionedto provide flat sides and the bearings are arranged so that the flatsides of the bearings 39 abut the edges of the lever 18 and the flatsides of the bearings 40. The bearings 39 are held from circumferentialand radial movement by the transverse flanges 41 and 42. The bearings 40are held from circumferential and radial movement by the transverseflanges 43. The construction is such that the inner brake shoe 2supports and holds the lever 18 from circumferential and radial movementand the lever 18 in turn supports and holds the outer brake shoe 3 fromcircumferential and radial movement and serves to spread apart the twobrake shoes.

I have also provided the axially extending pins 44 at the ends of thebody portions 16 of the brake shoes for assisting in supporting theouter brake shoe 3 on the inner brake shoe 2 and assuring parallelpositioning of the outer brake shoe relative to the inner brake shoeduring nonbraking periods. As shown in FIGURE 7, the pins have a pressfit with the body portion of the outer brake shoe and a sliding fit withthe body portion of the inner brake shoe.

The two brake shoes 2 and 3 are resiliently urged toward each other'andnormally held in retracted position by the generally U-shaped wiresprings 45 located in recesses in the opposed or facing radially outercorners of the bodies near their end portions. The springs 45 are heldin the recesses by the headed projections 46 which in the presentinstance are headed pins secured to the bodies, the arrangementproviding for easy assembly of the springs.

For the purpose of limiting the flexing of the brake drum 1 when thebrake shoes 2 and 3 are spread apart and into frictional engagement withthe disks 6 and 7 with sufiicient force to flex the brake drum, anabutment is provided for engaging the inboard of axially inner side I ofthe inner disk 6. In detail, the anchor bracket 5 has its arms 32extended axially through the central opening of the inner disk 6 andprovided with the integral radially outwardly extending projections 47formed with the axially outwardly opening cylindrical recesses 48. Theserecesses receive the cylindrical bosses 49 upon the arcuate stampedbacking 50 to which are secured the lining sectors 51 for engaging thesurface 52 on the axially inner side of the inner disk 6. The liningsectors, in addition to being operable to limit the flexing of the brakedrum,

also frictionally engage the inner surface 52 of the inner disk andserve in applying extra braking force to the brake drum when the brakeshoes 2 and 3 are forced against the disks 6 and 7 with sufficient forceto flex the brake drum. The rib 11 on the axially inner side of the disk6 encircles the backing 50 and the lining sectors 51 and assists inprotecting these parts from dirt and the like.

To axially adjust the lining sectors 51 to provide a predeterminedclearance between these sectors and the surface 52, the bosses 49 areinternally threaded and engaged by the screws 53 having the stems 54extending through the bottoms of the recesses 48. The bosses 49 areformed with an odd number of axial corrugations 55 and the screws areformedwith the diametral passages 56 in the ends of each of which arethe balls 57 resiliently urged outwardly by the coil springs 58. Duringthe turning of the screws, the balls of each screw alternately engagethe corrugations and serve to indicate a predetermined increment ofadjustment. In other words, the balls and corrugations serve to measurethe adjustment of the screws.

To manually adjust the inner and outer brake shoes 2 and 3 with respectto the disks 6 and 7, I have provided the adjustment screw 59 whichextends axially through I the central opening of the inner disk 6 andthreadedly engages the central portion 27 of the inner brake shoe andabuts the lever 18. 6G is a lock nut threaded on the screw and abuttingthe central portion of the inner brake shoe. Both the screw and nutextend axially inwardly a suflicient distance to be readily turnedmanually.

With the above construction, the various parts of the brake are simpleand may be economically manufactured and also may be readily assembled.During the assembling operation, the anchor bracket 5 is bolted on theflange 39 of the front wheel spindle after which the wheel hub 13 isassembled on the assembly. Also, the hydraulic cylinder is bolted to theinner brake shoe 2 and the inner brake shoe with the hydraulic cylinderin place, the outer brake shoe 3, the pairs of bearings 39 and and thelever 18 connected to the piston rod 22, which bears on the piston 21,are assembled and then secured together by the springs to form a unit.This unit is then inserted within the brake drum 1 with the brake shoesextending between the disks 6 and 7, after which the brake drum with theunit is mounted in place by passing the hydraulic cylinder and theradially inner central portion of the inner brake shoe through the notch61 of the fixed flange 14 or the wheel hub and through the space betweenthe arms 32 of the anchor bracket 5 and by engaging the extensions 34 ofthe inner brake shoe with the grooves 33 of the anchor bracket. Thebrake drum may then be secured to the fixed flange and the liningsectors 51 axially adjusted relative to the axially inner surface 52 ofthe inner disk 6. This is done by turning the screws 53 to move thelining sectors against the surface and then turning the screws in theopposite direction for a predetermined number of increments as measuredby the balls 57 engaging the corrugations to thereby secure apredetermined clearance. Also, the inner and outer brake shoes 2 and 3may be axially adjusted with respect to the disks 6 and 7 by means ofthe adjustment screw 59 and if desired the above ball and corrugationfeature may be used to secure the desired measured withdrawal adjustmentand predetermined clearance. In the event that the disk brake is for usewith a rear wheel of a motor vehicle, the anchor 5 is secured to asuitable axle flange at each rear wheel. It is also apparent that thebrake shoes 2 and 3 may be formed of some relatively weak material otherthan cast iron.

What I claim as my invention is:

1. A disk brake comprising a rotatable member having a pair of spacedrotatable disk surfaces, a pair of arcuate brake shoes movable axiallytoward said disk surfaces, said shoes being in the form of circularsegments of limited circumferential extent and having arcuate frica Y 7tion faces respectively engageable with said disk surfaces in responseto such movement thereof, said shoes being of a strong rigidconstruction to resist distortion, force applying means for forcingsaidv shoes axially toward said disk surfaces for pressure engagement oftheir friction faces with said disk'surfaces, said force applying meansacting on each shoe so that the'resultant force acts along a straightline which coincides with the centroidal axis of the arc of mean radiusof the friction face of each shoe 7 so that wear on the friction facesalong any radial line is uniform, said centroidal axis being spaced fromthe center of the are of the friction face of each shoe a distance equalto R sin /za a in radians where R is one-half the tume of the inner andouter radius of the arcuate friction face thereof, and a is the angle"bearing surfaces and having extended linear contact therewith.

- 2. A disk brake comprising a rotatable member having a pair of axiallyspaced disk members, a pair of arcuate brake shoes movable axially awayfrom: each other, said shoes being in the form of circular segments oflimited circumferential extent and having arcuate friction facesrespectively engageable with said disk mem bers in response to movementaway from each other, said shoes being of a strong, rigid constructionto resist distortion, force applying means for forcing said shoesaxially away from each other for pressure engagement of their frictionfaces with said diskrmembers, said'force applying means acting on eachshoe so that the resultant force acts along a straight line whichcoincides with the centroidal axis of the arc of mean radius of thefriction face of each shoe so that wear on the friction faces along a gbrake shoes between said disk members and movable axially'away from eachother, said shoes being in the form of'circular segments of limitedcircumferential extent and having arcuate friction faces respectivelyengageable with said disk members'in response to movement away from eachother, said shoes being of a strong, rigid construction to resistdistortion, force applying means for.

forcing said shoes axially away from each other for pressure engagementof their friction faces with said disk members, said force applyingmeans acting on each shoe so that the resultant force acts along astraight line which coincides, with the centroidal axis of the arc ofmean radius ofthe friction face of each shoe so that wear on thefriction faces along any radial line is uniform, said centroidal axisbeing spaced from the center of the arc "of the friction face of eachshoe'a distance equal to R sin /2a /2a in radians shoes, said leverhaving aligned pintles extending chordany radial line is uniform, saidcentroidal axis being spaced from the center of the arc of the frictionface of each shoe a distance equal to R sin /za /2 a in radians where Ris'one-half the sum of the inner and outer radius thereof andcoextensive with said ribs and having ex tended linear contacttherewith, an anchor supporting one of said shoes, said lever havingaligned pintles extenda ing chordwise of the brake, means pivotallyconnecting said lever pintles to saidanchor-supported shoe for thepivotal support of said lever by said anchor-supported shoe, and meanspivotally, connecting said lever pintles vto the other of said shoes forthe support ofsaid other shoe by said lever.

3. A disk brake comprising a rotatable member having a pair of axiallyspaced disk members, a pair of arcuate wise 0f the brake, meanspivotally connecting said lever pintles to said anchor-supported shoefor the pivotal support of said lever by said anchor-supported shoe,means pivotally connecting said lever pintles to the other of said shoesfor the support of said other shoe by said lever,- said 'means pivotallyconnecting said lever pintles to said respective shoes having axialslidable connection with said respective shoes, permitting relativeaxial movement between said lever and shoes said force applying meansalso including a hydraulic piston-cylinderassembly, the cylinder of saidassembly being fixed to said anchor-supported shoe, a rod connecting thepiston of said assembly to the radially inner end of said lever,'saidcam surface of said lever which contacts the rib of theanchor-supported shoe being located at the radially outer end of saidlever, said pintlesandsaid cam surface of said lever which contacts therib of said other shoe being locatedibetween the radially inner andouter ends of said lever, said rib of said other shoe being disposed ona line coinciding with the centroidal axis thereof.

Q References Cited by the Examiner V UNITED STATES PATENTS 1,749,745

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,190,398 June 22, 1965 Edwin R. Evans It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 7, line 18, for "tume" read sum column 8, line 27, strike out"an".

Signed and sealed this 30th day of November 1965.

(SEAL) A neat:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner ofPatents

1. A DISK BRAKE COMPRISING A ROTATABLE MEMBER HAVING A PAIR OF SPACEDROTATABLE DISK SURFACES, A PAIR OF ARCUATE BRAKE SHOES MOVABLE AXIALLYTOWARD SAID DISK SURFACES, SAID SHOES BEING IN THE FORM OF CIRCULARSEGMENTS OF LIMITED CIRCUMFERENTIAL EXTENT AND HAVING ARCUATE FRICTIONFACES RESPECTIELY ENGAGEABLE WITH SAID DISK SURFACES IN RESPONSE TO SUCHMOVEMENT THEREOF, SAID SHOES BEING OF A STRONG RIGID CONSTRUCTION TORESIST DISTORTION, FORCE APPLYING MEANS FOR FORCING SAID SHOES AXIALLYTOWARD SAID DISK SURFACES FOR PRESSURE ENGAGEMENT OF THEIR FRICTIONFACES WITH SAID DISK SURFACES, SAID FORCE APPLYING MEANS ACTING ON EACHSHOE SO THAT THE RESULTANT FORCE ACTS ALONG A STRAIGHT LINE WHICHCOINCIDES WITH THE CENTROIDAL AXIS OF THE ARC OF MEAN RADIUS OF THEFRICTION FACE OF EACH SHOE SO THAT WEAR ON THE FRICTION FACES ALONG ANYRADIAL LINE IS UNIFORM, SAID CENTROIDAL AXIS BEING SPACED FROM THECENTER OF THE ARC OF THE FRICTION FACE OF EACH SHOE A DISTANCE EQUAL TOSPS@ R SIN 1/2 A